1. Field of the Invention
The invention relates to a device and a working method for automatically changing the sets of rolls comprising work rolls, backup rolls and intermediate rolls of a single-stand or multi-stand strip rolling mill, by means of at least one roll changing carriage which can be displaced transversely with respect to the rolling stand into a changing position in line with the center of the strip stand. The carriage receives the sets of rolls that can be pulled out on guide rails running parallel to the rolls and displaces them transversely into a set-up position, in which the replacement with a new set of rolls takes place. A removal crossbar that supports the upper backup roll is provided for the removal of the set of backup rolls, which removal crossbar is supported on the lower backup roll when the work rolls and intermediate rolls have been removed and can be pulled out from the rolling stand together with the set of backup rolls.
2. Description of the Related Art
With the rolling stand, and as a result the entire rolling mill, at a standstill, there is of course a stoppage of production. This is particularly unfavorable if, upstream or downstream of the rolling mill, there are other plants, for example a pickling plant, which could actually continue running. The aim of each roll changing method is therefore to keep the downtimes of the rolling mill as low as possible.
In German Offenlegungsschrift DE 198 15 029 there is a description of a roll changing method for a rolling stand of a multi-stand strip rolling mill, the rolling stands of which have work rolls and backup rolls. After completing the rolling of a first metal strip, the rolling stand is stopped and the work rolls are removed. If the rolling stand has intermediate rolls, the intermediate rolls are preferably removed and installed together with the work rolls.
The backup rolls of this known strip rolling mill are changed with the aid of a removal crossbar in the form of a slotted backup roll changing frame, which is moved into the stand after removal of the set of work rolls. The work is largely carried out manually.
Another method and device for changing the work rolls and backup rolls of a strip rolling stand are described in DE 39 30 125 C2. Here, the changing of the rolls is performed to convert the rolling stand for example from a six-roll system, that is a rolling stand with work rolls, intermediate rolls and backup rolls, into a four-roll system, with work rolls and backup rolls. For removal of the sets of rolls, roll changing carriages which can be moved transversely with respect to the rolling stand and are equipped with guide rails and running rails for the removable sets of rolls are used. At least FIG. 4 of the drawing of this document shows the removal of the backup rolls with the aid of a removal crossbar which rests on the lower backup roll and supports the upper backup roll.
While the changing of the work rolls and also the intermediate rolls proceeds in a largely automated manner, in that, with the aid of the roll changing carriage and the corresponding pulling-out device, the sets of rolls are pulled out of the rolling stand onto the roll changing carriage, where they are brought into a replacement position by transverse displacement, the changing of the backup rolls largely takes place manually. The removal crossbar is brought between the backup rolls with the aid of a crane, the upper backup roll is set down onto the removal crossbar resting on the lower backup roll and the set of backup rolls is moved out on guide rails under the chocks of the lower backup roll. A large number of manual activities during the changing of the backup rolls and crane work require a long downtime of the rolling mill. In addition, the crane work is more dangerous than the automatic changing of the work rolls and/or intermediate rolls.